Conventionally, liquid crystal display panels have been increasing employed as image display devices for use in televisions, personal computers, personal digital assistants or cellular phones. Among these, a liquid crystal display device obtained by bonding a cover glass and a liquid crystal display panel using a transparent resin having a refractive index equivalent to that of the cover glass is advantageous in view of picture qualities such as contrast, color or clearness and in view of shock resistance of the liquid crystal display panel.
In a liquid crystal panel device of this kind, mixture of air bubbles when filling the transparent resin between the cover glass and the liquid crystal display panel will result in bright points at the time of incidence of light which remarkably degrades the picture qualities so that it is required to perform bonding without leaving any air bubbles between the substrates.
A generally known method for bonding two substrates such as a liquid crystal display panel and a cover glass using liquid transparent resin is the so-called inversion method. In the inversion method, as shown in FIG. 8, a liquid adhesive 102 is applied onto an adhesive surface of one substrate 100 of a pair of substrates 100, 101 to be bonded (FIG. 8A) and the substrate 100 is inversed to make the surface applied with the adhesive oppose an adhesive surface of the other substrate 101 (FIG. 8B). By approximate and pressure joining the substrates 100, 101 (FIG. 8C), the adhesive 102 is made to fit and spread between the substrates 100, 101 (FIG. 8D).
However, since the substrate applied with the liquid adhesive is inversed in the inversion method, it might by that dipping of the adhesive might cause scattering of the adhesive at the time of inversion or the like and that the adhesive adheres to spots other than the specified positions. Air bubbles are accordingly mixed at the time of adhering the substrates 100, 101, and such air bubbles will remain since it is impossible to fit and spread the adhesive between the substrates 100, 101 while eliminating the air bubbles. Moreover, the inversion method requires a larger-sized manufacturing facility the larger the size of the substrates to be adhered becomes which will lead to increased manufacturing costs.
Further, the so-called gap dispense method is a known bonding method of disk substrates such as DVDs. In the gap dispense method, as shown in FIG. 9, each of a pair of substrates 110, 111 to be bonded is held to face each other at a specified clearance (FIG. 9A) and a dispensing nozzle 112 is inserted between the substrates 110, 111 (FIG. 9B). An adhesive 113 is then injected from the dispensing nozzle 112 between both substrates while contacting these substrates (FIG. 9C) whereupon the adhesive 113 is dispersed over the entire clearance between both substrates by rotating both substrates 110, 111 (FIG. 9D).
According to this gap dispense method, it is possible to effectively prevent mixing of air bubbles at the time of bonding the substrates by supplying the adhesive 113 while making the adhesive contact the adhesive surfaces of both substrates that are held to face each other. Moreover, the gap dispense method is capable of dispersing, after injection of the adhesive, the adhesive over the entire surfaces of both substrates due to rotation of the substrates, of shaking off excess adhesive to the periphery, and of eliminating air bubbles.
However, when the gap dispense method is applied to bonding of large-sized substrates, the adhesive will not be dispersed through rotation but the adhesive will be fit and spread over the entire substrates by approximate the substrates since large-sized substrates have large adhesive areas and are of rectangular shape. Accordingly, the time required for fitting and spreading the adhesive will become longer accompanying the increase in size of the substrates which leads to a longer cycle time.
When a pattern for applying the adhesive by the dispensing nozzle is set to cover a wide area in order to shorten the time required for fitting and spreading, it might happen that an obstruction area is formed by the adhesive, leaving air bubbles. There are many restrictions for drawing patterns of adhesive for preventing occurrence of such obstruction areas so that the adhesive cannot be applied over a wide area of the substrates which consequently makes it difficult to shorten the time required for fitting and spreading.